MAGNESIUM ION-SELECTIVE OPTODES BASED ON A NEUTRAL IONOPHORE AND A LIPOPHILIC CATIONIC DYE

Flow-through type magnesium ion-selective optodes based on a neutral i onophore and a lipophilic cationic dye have been developed. The optode s were prepared by coating pellicular octadecylsilica beads with a lip ophilic organic liquid containing magnesium ionophores, a lipophilic c ationic dye and a lipophilic anionic additive, and packing the beads i nto a flow-through optical cell. Two neutral magnesium ionophores (K22 B5 and K22B1B5) and two novel lipophilic cationic dyes (KDC-1 and KDC- 2) were synthesized and tested for preparing the optodes. Among the de veloped optodes, an optode based on the ionophore K22B1B5 and a cation ic dye (KDC-2) produced the best magnesium ion optode with a relativel y high Mg2+ sensitivity and selectivity. This optode showed a fast and reproducible response to magnesium ion, even in a high concentration of background ions.